This invention relates to microwave stripline circuitry and, more particularly, to microwave stripline circuits that are used in forming magic tees.
Conventional microwave stripline magic tees, for example the so-called rat-race or 1.5 wave length circumference ring, are four-port, 3db coupling devices employed in converting a microwave input signal of a given power level into two either in-phase or 180.degree. out of phase output microwave signals, each of which output signals is at one-half the power level of the input signal. The rat-race devices have four arms that are connected to corresponding ports or terminals and are separated by 60.degree. of angular rotation from one another. Thus, for a common input arm, there are two output arms spaced one-quarter wave length away and a fourth terminated arm spaced one-quarter wave length away from one of the output arms and three-quarters wave length away from the other output arm. At center frequency, the power split from the common input arms to the two output arms is equal; however, the phase relationship between the two outputs is 0.degree.. Similarly, if power is fed in at the fourth arm, the power split to the two previously mentioned output arms is also equal; however, the phase relationship between the two outputs is 180.degree..
Although conventional stripline magic tees are satisfactory 3db coupling devices for splitting microwave input signals into in-phase or 180.degree. out of phase output signals of equal amplitude, at a design center frequency and over a narrow adjacent frequency band, they have not been effective for use as broad band (for example octave-wide) 3db couplers due to the fact that significant phase variations occur in the output signals as the input frequency departs from the design center frequency of the device.
It is, therefore, a primary object of the present invention to provide an improved microwave stripline magic tee.
Another object of this invention is to provide a microwave stripline magic tee capable of operating over a greater band width, for a given amount of output signal phase variation, than has heretofore been the case.
A still further object of the invention is to provide a microwave stripline magic tee capable of operating with a lesser amount of output signal phase variation, over a given narrow frequency band, than has heretofore been the case.
Additional objects and advantages of this invention will become apparent as the following description proceeds.